Extending Nitrogen Fixation Research To Farmers Fields

Nitrogen fixation by leguminous plants is especially important when farmers are trying to minimise fertilizer use for cost or environmental reasons. This second edition of the highly successful book, first published in 1991, contains thoroughly updated and revised material on the theory and practice of nitrogen fixation in tropical cropping systems.

Table 1. Global allocation of arable land between different com modities Globally, cereal cropping dominates cultivated land Commodities' Proportion of land area use (around 50% of total area, Table 1). The remain (%) ing arable land is used for production of oilseed, fibre, or food and cash crops. In addition, vast areas are Cereals maintained under temporary or permanent pasture for Wheat 16 forage production (2-3 fold greater than the total area Rice 10 under cultivation and permanent crop; Table 1, Fig. Maize 9 1). All cultivated crops, except for legumes (pulses All other cereals 13 and legume oil seeds) require the soil to provide rel Total 48 atively large amounts of nitrogen (N). It is necessary for the three most important cereals, wheat (Triticum Legumes aestivum), rice (Oryza sativa) and maize (Zea mays), Legume pulses 5 to take up 20 to 40 kg soil N ha -lover a period of 3 Legume oilseeds 6 to 5 months to satisfy the N requirements of the seed and supporting vegetative structure for each tonne of Total II grain produced (e. g. Fig. 2; Myers, 1988). Produc tive pastures on the other hand may assimilate> 100 Other crops I kg N ha- each annum, of which 50 to 90% will be Other oilseeds 6 consumed by livestock in intensively grazed systems Beverages / Tobacco 7 (Ledgardy, 1991; Thomas, 1995).

The turn of the millennium from the twentieth to the twenty-first century provides an occasion to review our understanding of a biological process, biological nitrogen fixation, that is of prime importance for the continued survival of mankind. This process has provided a basis for maintaining soil fertility since the beginning of organised agriculture, yet its very existence was confirmed only just over a century ago. In the intervening years, an enormous intellectual effort has dispersed much of the mystery surrounding biological nitrogen fixation. Biological fixation is widely exploited in agriculture, as are nitrogen fertilisers prepared for the last hundred years under extreme conditions of temperature and pressure. However, despite all our efforts, the fundamental nature of the reactions involved at the heart of the biological process remain unknown. This book aims to describe what we have learned in the last one hundred years or so about biological nitrogen fixation, about what its chemistry appears to be, and how it is applied in agriculture. This ambitious objective has not been attempted recently. It is aimed at students and those who wish to enter these very challenging areas of research, and who need to learn the state of the art at the turn of the millennium. The authors are all acknowledged world experts in their fields. They have prepared concise, well referenced and authoritative accounts of their subjects. This book provides a unique summary of the current state of knowledge that will be indispensable to all students and researchers, actual and potential, interested in biological nitrogen fixation.

Extended Versions of Papers Presented in the Symposium `Role of Biological Nitrogen Fixation in Sustainable Agriculture' at the 13th Congress of Soil Science, Kyoto, Japan, 1990

The symposium's objectives included an appraisal of the most recent studies relating to microbiological nitrogen fixation in tropical soils, consideration of aways and means of improving management of soils and crops in tropical farming systems to increase biological nitrogen fixation, of exploring ways of concurrently improving both legumes and other hosts and their symbionts to enhance nitrogen fixation, and of recommending the research needed and means of collaborating in the research effort.

Incorporating contributions from microbiologists, molecular biologists, plant breeders and soil scientists this volume reports the results and recommendations of an FAO/IAEA meeting of twelve experts on biological nitrogen fixation. This volume will be invaluable to scientists working on nitrogen fixation, soil microbiology, agronomy and crop production as well as farm advisers and extension specialists. Maximising the Use of Biological Nitrogen Fixation in Agriculture is unique in that it: -reviews the latest thinking on various aspects of biological nitrogen fixation technology and applications; -reviews the possibilities in enhancing nitrogen fixation in various cropping systems; -shows ways how biological nitrogen fixation can be used to enhance crop production; -considers the applicability of these technologies to small farmers in developing countries.